Short answer: for no-gi, yes — and for gi, you really should. After more than fifteen years on the mats and coaching at our own Melbourne gym, the rash guard is the one piece of kit we see new grapplers skip and then quietly regret. Here’s what it actually does, when you need one, and what the rules say if you’re competing.
What a rash guard actually does
A rash guard is a tight, stretchy top made from spandex-blend fabric that hugs the body. It isn’t about looking the part — it earns its place for three real reasons:
• Hygiene. Mats are a shared surface. A rash guard puts a clean barrier between your skin and the mat (and your training partners), which is your first line of defence against ringworm, staph and other skin nasties. This is the big one.
• Skin protection. “Rash guard” is literal. It stops mat burn, friction rashes and the gi-collar chafing that turns a good session into a sore week.
• Performance. A tight top gives your opponent nothing loose to grab in no-gi, wicks sweat so you don’t turn into a slip-hazard.
Gi BJJ: do you need one?
Technically optional — but we’d still say wear one. Under the gi, a rash guard (or fitted compression top) protects your skin from collar burn and keeps the inside of your gi cleaner between washes. On the rules: in IBJJF gi competition, men compete bare-chested, while women are required to wear a fitted top beneath the jacket. For everyday training, a rash guard under the gi is simply good practice.
No-gi BJJ: non-negotiable
In no-gi there’s no jacket to soak up sweat or protect your skin, so the rash guard becomes essential — for hygiene, for grip-free fabric, and because most gyms and every IBJJF competition require it. If you only buy one, buy a good no-gi rash guard.
Long sleeve or short sleeve?
Both are legal and both work — it comes down to coverage and climate. Long sleeves give you the most skin protection (more barrier against mat burn and infection) and are the most popular for competition. Short sleeves run cooler, which plenty of grapplers prefer through an Australian summer. Many of us own both and pick by the session.
The IBJJF rules (if you’re competing)
This is where people get caught at uniform check, so get it right. Under the IBJJF no-gi ruleset, your rash guard must be:
• Skin-tight elastic material that covers your torso all the way to the waistband of your shorts — no loose or baggy tops, and no sleeveless.
• Coloured black or white, and displaying at least 10% of your belt rank colour. A rash guard that’s 100% your rank colour is also fine.
• Short or long sleeve — both allowed; sleeveless is not.
The colour detail that catches people out
Here’s the part almost nobody explains. The IBJJF doesn’t just say “blue” or “purple” — it specifies an exact shade for each rank, using Pantone references. Pantone (you’ll see it written as “PMS”) is the standardised colour-matching system designers and manufacturers use, where every colour has one precise code — so there’s no arguing whether your rash guard is “blue enough.” It’s either the right shade or it isn’t.
For the adult belt ranks, the IBJJF’s official references are:
• White — PMS White
• Blue — PMS 2172 C
• Purple — Violet C
• Brown — PMS 469
• Black — Black C
(Kids’ ranks have their own references too — grey, yellow, orange and green.) Purple is the classic trap: a rash guard that looks purple to you can easily be the wrong purple at uniform check. The safe move is to buy a rash guard made specifically as an IBJJF ranked rash guard in your belt colour, rather than guessing with a generic one — and to confirm the current shades on the official IBJJF uniform page before you compete.
What to look for in a good one
• Flatlock seams so the stitching doesn’t dig in or chafe over a long roll.
• A proper compression fit — snug, not loose — so there’s nothing to grab and it stays put through scrambles.
• Breathable, quick-drying fabric that survives constant washing without going see-through or losing its stretch.
The bottom line
For no-gi, a rash guard isn’t optional — it’s the core of your uniform. For gi, it’s the small habit that keeps your skin and your training partners healthier. Buy one that fits properly, wash it after every session, and if you compete, match it to your rank in the right shade. Our BJJ & no-gi rash guards are designed in Melbourne, tested on our own mats, and built with the seams and fit that actually hold up. (New to sizing? Our gi sizing guide covers that side too.) Browse the range and find yours.
